Problem: $ { {0} \times \left[\begin{array}{rr}{4} & {0} \\ {-2} & {4} \\ {-1} & {-1}\end{array}\right] = {?} } $
Answer: To multiply a matrix by a number, multiply each item of the matrix by the number. ${\left[\begin{array}{rr}{0}\times{4} & {0}\times{0} \\ {0}\times{-2} & {0}\times{4} \\ {0}\times{-1} & {0}\times{-1}\end{array}\right]}$ Now, simplify: ${\left[\begin{array}{rr}{0} & {0} \\ {0} & {0} \\ {0} & {0}\end{array}\right]}$